Neuronal signalling 1.docx

2 types of synapses Chemical No direct contact between pre and post synapse Chemical signal released from axon terminals e.g. acetylcholine Acts on dendrites and receptor Electrical Known as gap junctions. Direct contact between cells Allows synchronisation e.g., contraction of heart. Found in muscl...

2 types of synapses Chemical No direct contact between pre and post synapse Chemical signal released from axon terminals e.g. acetylcholine Acts on dendrites and receptor Electrical Known as gap junctions. Direct contact between cells Allows synchronisation e.g., contraction of heart. Found in muscles and neurons. Action potential depolarised end terminals of presynaptic membrane Voltage gated Ca2+ channels open and Ca2+ enter the presynaptic neurone. Causes release of vesicles that contains the neurotransmitters via exocytosis. Neurotransmitter travels across synaptic cleft and binds to receptors on post synaptic neurone. When the neurotransmitter binds to the sodium channels on post synaptic neurone, it causes the sodium channels to open and release sodium ions which causes it to depolarise and action potential can then carry on. An EPSP is when only couple of channels open which isn’t enough as it doesn’t reach the threshold value. What is a EPSP? An excitatory post synaptic potential is when a single ion channel is opened which isn’t enough to reach to the threshold potential to trigger a AP. What is ISPS? An inhibitory post synaptic potential is when a single ion channel such as Cl- which is negative therefore making the membrane more negative therefore less likely to trigger an AP. Temporal Summation Constant firing of EPSP’s to reach the threshold value. Spatial summation Different EPSP’s add up together to reach threshold value. Presynaptic Inhibition Allows extra level of control. Neurons as networks Multiple inputs to each neurone Whether an AP is generated depends on Excitatory inputs Inhibitory inputs Neuromodulator inputs Presynaptic inhibition Synapses are plastics. Synaptic plasticity- the ability of synapses to change the strength of their connections. Long term potentiation (LTP)- persistent increase in synaptic strength Long term depression (LTD)- persistent decrease in synaptic strength VEY IMPORTANT FOR MEMORY